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MX
112
S.B.
No.
2
AM NOISE REDUCTION MODIFICATION
MODEL:
MX
112
FM/AM Tuner-Preamp
PURPOSE OF MODIFICATION:
To
improve AM signal
to noise ratio.
WHAT UNITS ARE AFFECTED:
Serial
No.
10S01
to 43S90 Only.
WHEN MODIFICATION SHOULD BE MADE:
When customer complains that AM
is noisy on
local
stations or that sensitivity
is poor.
MclNTOSH MODIFICATION KIT NO.:
No kit.
PARTS REQUIRED:
QUANTITY
PART NUMBER
1
061-043
PROCEDURE :
Step
1
Remove bottom cover, Multiplex-AM top cover, and RF
front end bottom cover.
Remove capacitors C204 and
C208 on AM PC board.
See service manual
for exact
location.
Replace top cover.
Step
2
Locate Q4, AM RF amp 1 ifier
in RF front end chassis.
Connect the
.OlpF disc capacitor between the source
terminal
of Q4 and the ground
lug of the terminal
strip as shown
in the accompanying sketch.
Replace
bottom covers.
Step
3
Check performance.
If dial
calibration
is off at
high end of the band,
perform AM alignment steps
3 and 5 in service manual.
The top cover of the
RF front end
is
removed for access to the align-
men t t rimme rs.
(over)
oo
•
x
z
o
DESCRIPTION
•OlpF +80-20% Disc capacitor
#*>
SERVICE BULLETIN
McIntosh Laboratory Incorporated
2 Chambers Street
Binghamton, New York 13903
Phone: Area Code 607-723-3512
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